Without limiting the scope of the present invention, its background is described with reference to sealing in high temperature steam applications, as an example.
It is well known in the oil and gas extraction art that an O-ring may be used to form an effective seal between two cylindrically shaped parts that cooperate in either a static or dynamic environment. Typically, one of the cooperating parts will include a gland groove in which the O-ring type seal is placed. In order to establish the desired seal between the two parts, the O-ring must be under contact stress with both parts during operations. According to one common practice, the O-ring gland groove is disposed on the inner cooperating part and has a diameter slightly larger than the inner diameter of the O-ring and wider than the cross section of the O-ring. This design provides the desired contact stress to the O-ring and allows axial movement of the O-ring as it is inserted into the sealing area.
It has been found, however, in certain high temperature installations, that the useful life of such a single O-ring in a gland groove is limited. This is due, in part, to the tendency of the elastomeric O-ring materials to extrude into the clearance gap between the cooperating parts. To overcome this deficiency, use of a packing stack or sealing array that includes a centrally disposed O-ring seal and one or more O-ring support members positioned on either side of the O-ring, has been attempted. The O-ring support members, which are also referred to as backup rings, commonly include V-rings, which are V-shaped or Chevron type packing rings with a concave, V-shaped bottom surface, a convex top surface and straight sides. According to this practice, the centrally disposed O-ring and the backup rings work together to provide the desired seal, with the aforementioned clearance gap being filled by the backup rings, thereby preventing O-ring extrusion.
It has been found, however, that in very high temperature applications, such as steam applications, the useful life of conventional sealing arrays is limited. For example, that material of the O-ring seals tends to diffuse into or become integrally bonded with the material of the adjacent V-ring seals, resulting in a loss of the round cross section of the O-ring seals. This loss of geometric integrity not only limits the sealing capability of the O-ring itself but also limits the O-ring's ability to energize the V-rings, thereby reducing or eliminating contact at the sealing boundaries.
Therefore, a need has arisen for a sealing array that provides the desired sealing functionality between cooperating parts. A need has also arisen for such a sealing array that is capable of maintaining the desired sealing functionality in high temperature applications. Further, a need has arisen for such a sealing array that is capable of maintaining the desired sealing functionality in very high temperature applications including steam applications.